Save the RDAP request time globally instead of passing it around

Also removed the rdapWhoisServer value, as it's just null and will likely stay that way (it isn't mentioned in the RDAP response profile)

If it'll ever become required, we can add it back.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=247643981

java/google/registry/config/RegistryConfig.java

@@ -969,20 +969,6 @@ public final class RegistryConfig {
       return 100;
     }
 
-    /**
-     * WHOIS server displayed in RDAP query responses. As per Gustavo Lozano of ICANN, this should
-     * be omitted, but the ICANN operational profile doesn't actually say that, so it's good to have
-     * the ability to reinstate this field if necessary.
-     *
-     * @see google.registry.rdap.RdapActionBase
-     */
-    @Nullable
-    @Provides
-    @Config("rdapWhoisServer")
-    public static String provideRdapWhoisServer() {
-      return null;
-    }
-
     /**
      * Redaction text for email address in WHOIS
      *